Hyperthermia or heat stroke is an ongoing threat to animals and children confined within enclosed vehicles and other extreme environments, especially during the warmer summer months. Soldiers, working military animals, companion animals and livestock may also be at risk of hyperthermia when living or working in extreme environments. For example, the temperature inside of the passenger section of a parked automobile may rise above 105° F. in less than 10 minutes and when the ambient outdoor temperature is greater than 88° F. Ambient temperatures routinely exceed 105° F. in some military deployment sites such as desert military stations.
To avoid hyperthermia in extreme environments, body temperature may be regulated by disposing of excess heat generated by exertion and/or basal metabolic activity. Conduction of internally generated heat to external body surfaces and evaporative cooling of surface fluids such as sweat are typically the primary means for animals to regulate body temperature. In some animals such as canines that do not generate sweat, respiratory evaporation may be the dominant mechanism of heat loss for body temperature regulation. The effectiveness of body temperature regulation in animals, in particular the efficiency of evaporative cooling, is sensitive to ambient environmental conditions.
High ambient temperatures and elevated humidity reduce the effectiveness of body temperature regulation. Regardless of temperature, when relative humidity exceeds 80% in an environment, the effectiveness of evaporative cooling is substantially reduced. High relative humidity in the ambient air around an animal may be a more critical factor than high temperature with respect to risk of hyperthermia, especially in animals such as canines that rely solely on respiratory evaporation for body temperature regulation.
Existing products monitor animals for signs of hyperthermia by measuring the ambient temperature inside of an enclosed environment such as the passenger compartment of an automobile. However, these existing devices generally only measure ambient temperature inside of the vehicle and fail to accurately measure or otherwise estimate the actual core or skin temperature of the animal. Further, these devices fail to account for variability in an animal's reaction to an extreme environment due to physiological factors, such as the animal's activity level, that may also vary depending on the particular species of animal.
A need exists in the art for a system for monitoring the condition of animals in extreme environments in which both environmental and physiological quantities are measured and processed to assess the animal's risk of developing a dangerous condition such as hyperthermia. A need in the art further exists for a monitor system, that include empirically-derived algorithms to estimate the condition of the animal based on environmental measurements, such as ambient temperature and relative humidity, and physiological measurements such as the animal's skin temperature and activity level. In addition, a need in the art exists for a monitor system that monitors a subset of a plurality of environmental and physiological sensor signals, in which the subset of signals includes non-redundant and/or high-quality signals. Such a system would be able to discern when an animal in an extreme environment is at risk of developing a dangerous condition such as hyperthermia or hypothermia and issue an alert to a caregiver or emergency response entity.